As discussed in (for example) U.S. Pat. No. 6,708,557 to Moskwa et al. (which is incorporated by reference herein, and thus should be regarded as a part of this document), the single-cylinder test engine (1CTE) has long been an important and widely-used tool in engineering and development of internal combustion engines. The 1CTE is typically a single cylinder, piston and head taken from a multi-cylinder engine (MCE), or having a design adapted from a MCE, and which is used to simulate performance of an MCE on a smaller and simpler scale. Since the 1CTE has only a single cylinder, it is generally much easier to install and use measurement instrumentation in a 1CTE than an MCE, thereby allowing more complete data collection regarding a cylinder's fluid dynamics, heat transfer, thermodynamics, emissions and other characteristics. Additionally, owing to the simpler design of 1CTEs, they are much less expensive and time-consuming to build and modify when working out design challenges associated with combustion chamber shape, timing, or other geometric and thermodynamic issues, or to experimentally validate theoretical/computational performance predictions.
However, 1CTEs also carry numerous drawbacks. The contributions of the missing cylinders are sometimes critical to accurate simulation of MCE performance. U.S. Pat. No. 6,708,557 describes the use of a high-bandwidth transient dynamometer wherein a processor (e.g, a computer, application specific integrated circuit, or other calculating device) simulates the inertial contribution of additional “virtual” cylinders added to a 1CTE, and causes the dynamometer to apply appropriate loads or energy inputs to the 1CTE such that the 1CTE behaves as if the virtual cylinders were physically present within the 1CTE (i.e., as if the 1CTE was a MCE).
However, while this system is extremely useful for adapting a 1CTE to simulate the inertial dynamics of an MCE, it has been found that the “missing cylinders” of the 1CTE also have other performance contributions that are usefully taken into account if the 1CTE is to fully represent MCE performance—in particular, the gas exchange characteristics of the 1CTE versus those of an MCE (i.e., the “breathing” of an engine, particularly during its intake and exhaust cycles). To illustrate, if a 1CTE is mounted on a production manifold (a manifold of a type that would actually be used with the MCE which the 1CTE is to represent), the intake valves of the 1CTE draw air from the manifold without experiencing any effects from the intake valves of other cylinders: the airflow dynamics of the manifold are almost entirely dependent on the intake of the 1CTE. In contrast, in an MCE, air is usually drawn into the intake ports of several cylinders at the same time, and thus the pressure, volumetric flow, etc. at the intake port of one of the cylinders is affected by the conditions at the intake ports of the other cylinders. The interaction between the intake ports has a substantial effect on the performance of each cylinder of the MCE, particularly during transient operation of the engine (i.e., at non-constant speed/load conditions). It would therefore be extremely useful to have available some means of modifying a 1CTE to experience the same gas exchange characteristics that the 1CTE would experience if the 1CTE was actually present as a part of an MCE, so that a 1CTE could more accurately simulate MCE performance.